1. Field of the Invention
The present invention relates generally to an apparatus and method for renewal-based resource allocation in a Broadband Wireless Access (BWA) system, and more particularly, to an apparatus and method for renewal-based resource allocation so as to minimize the amount of downlink/uplink control information required for resource allocation.
2. Description of the Related Art
In general, the developmental works of communication systems have focused on voice service. These communication systems are currently under development to additionally provide data service and a variety of multimedia services beyond voice service. A voice-oriented communication system has limitations in meeting ever-increasing user demands for services because of relatively narrow bandwidth and high price. In addition, with the development of communications technology and the increasing user demands for Internet service, there is an increasing need for a communication system that efficiently provides Internet service. In response to these needs, a BWA system has been introduced to provide an efficient Internet service in a band broad enough to meet the rapidly increasing user demands.
The BWA system is designed to support standard voice service as well as a variety of low-speed and high-speed data services and multimedia application services including high-quality moving pictures in an integrated fashion. This BWA communication system allows for connectivity to a Public Switched Telephone Network (PSTN), a Public Switched Data Network (PSDN), Internet, an International Mobile Telecommunications2000 (IMT2000) network, and an Asynchronous Transfer Mode (ATM) network through wireless media using broad bands of 2, 5, 26, and 60 GHz under a mobile or fixed environment. The BWA communication system also provides a channel transmission rate of about 2 Mbps or higher. BWA systems are classified into a broadband wireless subscriber network, a broadband mobile access network, and a high-speed Wireless Local Area Network (WLAN) according to terminal mobility (fixed, mobile), communication environment (indoor, outdoor), and channel transmission rate.
International standardization organizations, Institute of Electrical and Electronics Engineers (IEEE) 802.16 and IEEE 80.20 groups, are currently developing the standardization of wireless Access for the BWA system. The BWA system adopts Orthogonal Frequency Division Multiplexing (OFDM)/Orthogonal Frequency Division Multiple Access (OFDMA) for physical channels. Since a physical channel signal is transmitted on a plurality of subcarriers in OFDM/OFDMA, high-speed transmission is enabled.
The BWA system transmits information concerning resources allocated to each user and the operation mode of the resources by a MAP or on a broadcasting channel, such as, for example, a shared signaling channel. The operation mode information may include information about a channel coding type, a coding rate, a Hybrid Automatic Repeat reQuest (HARQ) type, or a Multiple-Input Multiple-Output (MIMO) scheme.
As services provided by communication systems have evolved from voice to data, resource allocation has become more complex. For voice service, resource allocation is relatively simple because the voice service is a circuit-switched service and thus a certain amount of resources are allocated to a particular user during a session. In contrast, since the data service is a packet-switched service, resources should be dynamically allocated while a session is maintained, thereby rendering resource allocation complex. The complex resource allocation leads to an increase in the amount of resource allocation information that is periodically or non-periodically provided to users. In particular, a system aiming at high-speed wireless communication service has many factors that increase the amount of resource allocation information, inclusive of a short scheduling period and a dynamic selection of a modulation scheme according to channel status. Hence, a resource allocation information transmission mechanism significantly affects system throughput.
In a conventional IEEE 802.16e system, a Base Station (BS) broadcasts downlink/uplink information required for Mobile Stations' (MSs') access to the BS in every resource allocation duration. The information is collectively called MAP information, and individually a downlink MAP (DL-MAP) and an uplink MAP (UL-MAP). The MAP information is delivered at the start of a frame. Upon receipt of the MAP information, an MS interprets the MAP information and accesses the BS on the downlink and uplink in bursts indicated by MAP Information Elements (IEs), i.e. DL/UL-MAP IEs included in the MAP information. To be more specific, the MS monitors the existence of its Connection Identifier (CID) in the DL/UL-MAP IEs. In the presence of the CID, the MS transmits/receives data based on additional information included in the DL/UL-MAP IEs such as operation mode information. If resources are continuously allocated to the MS as with a circuit-switched service, the BS has to transmit resource allocation information to the MS every allocation duration.
In accordance with IEEE 802.20 Mobile Broadband Frequency Division Duplex (MBFDD)/Mobile Broadband Time Division Duplex (MBTDD) draft, resource allocation information for each user is transmitted in a separately procured encoding block in every physical frame (resource allocation unit). As illustrated in FIGS. 1A and 1B, various pieces of allocation information are distinguished by headers. For each resource allocation mode, a sticky channel allocation scheme is characterized in that once particular radio channel resources are allocated to an MS, they are maintained until the allocation is released. Thus, if allocated resources are kept, the amount of resource allocation can be reduced. However, during the temporary absence of transmission data in allocated resources dedicated to the MS, the resources are used just for the MS to notify that the connection is kept rather than for other users. That is, the resources are wasted. Also, sticky channel allocation and non-sticky channel allocation should be distinguished for each resource allocation mode, thus increasing the bit number of a header for mode identification.
Accordingly, there exists a need for a resource allocation method, which if continuous resource allocation is required for a user, obviates the need for transmitting resource allocation information with a large overhead each time and allows resources of the user to be used for another user, when the user is placed in a short idle period.